Jerry Hey wrote:

Paul, what size fuel injectors do you recommend.  Doing the calcs

for

225 hp and .65 BSFC  comes out to 47lb./hr.  I don't really expect

to

see 225 and I am hoping the .65 is too high too.     Jerry

We are using MSD 50 pound injectors. PN 2013. Can be bought from

Summit

www.summitracing.com

Paul Lamar

Paul / Jerry,  thats 50lb/hour per injector right.  We're using 2 per

runner so shouldn't we be looking at 25 to 30lb/hour per injector?
Which gives a total of 50 or 66lb/hour at WOT.  Or am I missing
something?  Tom Webber


At .65 BSFC full rich and 250 HP that is 130 pounds an hour.
At .65 BSFC full rich and 300 HP that is 195 pounds an hour.
I ain't taking any chances :) I am using four 50 pound units.
There is little or no difference in price and most all are
interchangeable.

Paul Lamar

Ben Schneider wrote:

What happens if you put in too big of injectors? Will you use more fuel, or
do you change duration in the EC2 somehow?

  Ben Schneider
    N713R   RV7 Renesis   (not at that point yet, but listening intently)

IMHO that is exactly what happens when you edit the map in Tracy's computer.
You use a mixture monitor that works off the O2 sensor to set the
injector pulse width. Injectors have a limited dynamic range.
In other words they only work well from about 10% on to about 80% on
more or less. After that they lose linearity. Therefore Mazda and Tracy 
use two sets of two injectors. Four total. Also gives a bit of redundancy for
safety reasons.

Only the primary injectors are used up to about the half HP point roughly
and then they run wide open (80% duty cycle). At that point the duty
cycle of the secondary injectors are progressive increased up to
maximum potential HP. Hopefully they never reach 80% as then the fuel
deliver starts to drop off with further HP increases and the engine 
could go lean.

Is that about right Tracy?

BTW the high power RX8 engine uses six injectors.
 
Paul Lamar
 
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